Presently, a study has been progressed about study about a chemical vapor deposition using a various metallic oxide of Indium, Tin, Zinc, Titanium and Cesium, magneton sputtering and a reactive evaporation as a method for preparing transparent electrode at home and abroad. But the study has a demerit resulting in high process cost in order to coat to a metal oxide on the substrate because coating metallic oxide to substrate needs to vacuum condition.
As a method for preparing transparent electrode processed at lower cost, a method for using conductive polymers has been become influential. The electrode processed by using conductive polymers is good for decreasing the process cost and working process because it is capable of using a various existing method for a coating polymer.
In case of manufacturing a flexible display or a electrical light device, when the transparent electrode processed with the conductive polymers such a polyacethylene, polypyrrole, polyaniline and polythiophene is compared with the transparent electrode processed with a Indium Tin Oxide (ITO), it takes advantage of the process, and in case of need for a very flexible electrode, particularly manufacture of touch screen, the transparent electrode processed with the conductive polymers is good for increasing a life time. The transparent electrode have many merits, but generally conductive polymers increases a sheet resistance in case of slightly coating layer in order to increase the transmittance so that conductive polymers absorb a ray in the visible rays area and the conductive feature of organic electrode manufactured by the conductive polymers is increased in proportional to the thickness of the electrode. Therefore the conductive polymers is difficulty in applying to a applicable field of the transparent electrode such a touch panel, flexible display. Particularly in order to improve the process of the conductive polymers, when the transparent electrode is manufactured with the method, wherein the conductive polymers is pulverized to the nano-sized particle and uses commercially available dispersed polythiophene, it shows about 1□/sq of sheet resistance. Therefore it is difficulty in using with the transparent electrode using for displaying in the condition of 85% of transmittance.
U.S. Pat. No. 5,766,515, U.S. Pat. No. 6,083,635 and Korean Patent Publication NO. 2000-1824 disclose a method for improving the conductivity of electrode manufactured with the aqueous solution of polyethylenedioxythiophene (PEDOT) conductive polymers having nano-sized particle by using a solvent or a additive. But U.S. Pat. No. 5,766,515 or U.S. Pat. No. 6,083,635 has a problem as following, when a polyhydric alcohol, e.g sorbitol is added, the sheet resistance of coating layer having more than 90% transmittance is difficult to decrease less than 1 □/sq, and when a amide solvent is added, the sheet resistance of coating layer can be decrease less than 1 □/sq, but a hardness of layer is low and coating feature is diminished. On the other hand, according to Korean Patent Publication NO. 2000-1824, when a silicasol is added to aqueous solution of polythiopene treated with the amide solvent, the hardness of layer is improved, and the sheet resistance is increased more than 1 □/sq in case of improving the hardness of layer.
To consider above the feature, the coating layer shows more than 90% of the transmittance and less than several hundred Ω/sq of the sheet resistance, also has the excellent transparency and hardness and the low resistance. Therefore a development of organic transparency electrode material which can apply to a electronic equipment has been needed continually.